The present invention relates to a method for manufacturing a pneumatic vehicle tire by producing a green carcass on a cylindrical carcass building drum with at least the following steps:
a) applying the inner liner onto the cylindrical carcass building drum, PA1 b) applying at least one carcass ply, containing textile reinforcement elements or comprised thereof, whereby the ends of the applied carcass ply have an overlap zone, PA1 c) positioning the bead cores, PA1 d) subsequently completing and vulcanizing the green tire in a conventional manner. PA1 a) providing a cylindrical building drum with a bar or a depression having a longitudinal extension in a direction parallel to the orientation of reinforcement elements of a carcass ply to be applied to the building drum; PA1 b) positioning a lining on the cylindrical building drum; PA1 c) placing at least one carcass ply, comprising reinforcement elements and having a leading end and a trailing end, onto the lining such that the leading end and the trailing end overlap in an overlap zone at the bar or the depression, thereby forming an overlength of the reinforcement elements in the overlap zone for preventing a constriction of the overlap zone within the vulcanized, inflated tire; PA1 d) completing the green tire on the building drum; PA1 e) vulcanizing the green tire. PA1 a) positioning a lining on the cylindrical building drum; PA1 b) placing at least one carcass ply, comprising reinforcement elements and having a leading end and a trailing end, onto the lining such that the leading end and the trailing end overlap in an overlap zone; PA1 c) folding the carcass ply in the overlap zone into a least one fold to form an overlength of the reinforcement elements in the overlap zone for preventing a constriction in the overlap zone within the vulcanized, inflated tire; PA1 d) completing the green tire on the building drum; PA1 e) vulcanizing the green tire.
For the manufacture of a vehicle tire the individual components of the tire are sequentially wound onto the building drum. The individual plys are cut to strips that have a length reaching once around the drum circumference. When winding the individual strips, it is, in general, desired that the ends of each strip overlap in order to ensure that after producing and vulcanizing the green tire there are indeed closed plies in the circumferential direction which ensure the proper functioning of the finished tire.
Therefore, when applying the carcass ply, which especially in passenger car tires is comprised mostly of textile reinforcement elements embedded in rubber material, the trailing and leading ends of the applied carcass ply are overlapped. In the overlap zone (approximately 2-6 mm wide) a doubling of the material thickness is thus provided. Accordingly, the textile reinforcement elements are also present with double density. These reinforcement elements extend, for example, in the manufacture of radial tires, transverse to the circumferential direction of the building drum, and may be comprised of, for example, rayon, polyester or other organic reinforcement elements. Polyester has the advantage that it is less expensive. However, reinforcement elements consisting of polyester have the disadvantage that they have a higher stretching ability. At the overlap zone of the carcass ply in which, as mentioned above, a higher reinforcement element density is present, the same force load results in reduced stretching of the carcass ply within the overlap zone, in comparison to other carcass ply zones, when the tire is inflated because of the changed modulus of elasticity withing the overlap zone. In the inflated state of the tire, the seam is thus visible as a constriction within the sidewall. The quality and stability of the tire is not affected by this, however, this is a visual defect which especially by laymen is interpreted as a rupture within the carcass so that the tire is returned to the tire or the vehicle manufacture as a defective tire.
It is therefore an object of the present invention to prevent the constriction of the tire within the sidewall area.